1. Field of the Invention
The invention is situated in the field of materials handling technology and it concerns a method and a device serving for transforming a supply stream, in which flat stream elements are conveyed with their flat expanse aligned essentially parallel to the conveying direction and in particular overlapping one another. The method and the device in particular serve for transforming a supply stream being conveyed in a loosely supported manner and comprising, as stream elements, groups of flat objects (e.g. printed products) having different formats and lying loosely on top of one another, the groups overlapping one another. This supply stream is transformed into a conveying stream, in which the groups again are conveyed loosely supported, but are at a distance from one another, so that, for example, they can be supplied to a packaging operation using a packaging material supplied from a roll.
2. Description of Related Art
Transformation of a supply stream (imbricated stream), in which individual, flat objects, such as printed products, are conveyed overlapping one another, into a stream in which the objects are conveyed behind one another and, if so required, at a distance from one another, is, according to the state of the art realized by accelerating the objects such that their spacing becomes greater than their expanse in the conveying direction. This method is unproblematic if the flat stream elements are stable and the conveying rates (in elements per unit of time) are not very high. For high conveying rates and for stream elements that are relatively long in the conveying direction, such methods give very high conveying speeds, and starting from a supply stream-with a high degree of overlap necessitates also high accelerations, for the mastering of which in particular not very stable stream elements, for stabilization, are gripped at their leading edge.
In order to circumvent the difficulties mentioned above, it is also proposed to split up an imbricated stream of the type mentioned into part streams, wherein at a switch-point stream sections are alternately supplied to one or the other of the part streams from the leading end of the imbricated stream, the stream sections being groups of overlapping stream elements. By subsequent suitable transformation, the partial streams can be made into streams in which the stream elements are conveyed one behind the other and which, due to the reduced conveying rate resulting from the splitting-up, are conveyed at a speed that is correspondingly lower than in the case described above.
The sections of the imbricated stream alternately assigned to each part stream usually are deviated from the main stream in a direction transverse to the principal surfaces of the flat stream elements (for a loosely supported imbricated stream: downwards or upwards), which deviation can be realized using a very simple device, such as a pivoting conveying substrate.
If an imbricated stream is to be directly transformed into part streams (i.e. without further transformation of the part streams) in which the stream elements are conveyed without overlap, i.e. behind one another and at a distance from one another, it is necessary to deviate from the imbricated stream not streams sections comprising a plurality of overlapping elements each, but rather individual elements. For this purpose, every element has to be gripped individually prior to the splitting-up, usually with the help of two gripper conveyors, as, for example, described in the publication EP-1063187 (or U.S. Pat. No. 6,401,903), one gripper conveyor being assigned to each longitudinal edge of the imbricated stream and one gripper conveyor being arranged on each side of the stream. In a gripping zone, the gripper conveyors run parallel to the imbricated stream, and downstream of the gripping zone they diverge. The gripper conveyors are operated in synchronism with the imbricated stream such that the grippers of one of the conveyors grip every second stream element from one side (longitudinal edge zone of the stream) and the grippers of the other conveyor grip the other stream elements from the other side. The gripped stream elements are then moved apart by the diverging gripper conveyors and are then, for example, transferred to further conveying means.
For splitting an imbricated stream as described in the last paragraph it is necessary that the two opposite edges of the flat stream elements situated on both sides of the imbricated stream can always (for all stream elements) be gripped in the same way. This means that these edges of all stream elements need to be positioned the same way in the imbricated stream. Or it means that the supplied, overlapping stream elements all have to have the same width. Splitting into more than two partial streams is not possible. For being able to grip individual stream elements it is further necessary that in the imbricated stream to be split-up the overlap of the stream elements is such that there are locations without overlap. If this condition is not fulfilled, the leading stream element needs to be laterally moved away from the supply stream before the next stream element can be gripped, which in particular in the case of stream elements of little stability is very difficult to implement.
For splitting imbricated streams by deflecting individual stream elements, it is also possible to grip the leading edge of the one stream element positioned at the leading end of the imbricated stream, as described in the publication EP-1155992. These leading edges are alternately gripped by the grippers assigned to the part streams to be established, and the gripper tracks diverge downstream of the gripping zone. For such splitting methods, the same severe conditions apply for the leading stream element edges as is the case for the lateral element edges in the method described further above. On the other hand, however, this method makes it possible to split the imbricated stream into more than two part streams. Because the leading edge of an element can only be gripped when the preceding stream element is situated at a distance from the leading end of the imbricated stream, on splitting a loosely supported stream, pairs of downstream and upstream elements have to be moved relative to one another, when only the downstream element is held gripped but not the upstream one. This can become a problem if the stream elements are unstable.
As long as the stream elements being conveyed in the imbricated supply stream are individual flat objects of the same format overlapping one another in a regular manner (regular scale spacing), the conditions as mentioned above to be fulfilled by the supply stream for being able to be split by gripping and leading apart individual stream elements according to the methods of the state of the art do not represent a problem. Even when groups of objects of the same format lying stacked one upon the other constitute the overlapping stream elements of the imbricated stream, there are no significant difficulties due to these conditions. If, however, the overlapping stream elements of the imbricated stream are groups of flat objects lying loosely upon one another and having differing formats and shapes and/or being stacked non-uniformly, it becomes considerably more difficult or even impossible to create an imbricated stream in which the mentioned conditions are fulfilled. This is in particular the case, because it is necessary, that in every gripped group all objects are gripped, but no object of a preceding or following group is gripped also.
It is an object of the invention to create a method and a device to transform, with simple means, a supply stream of stream elements (individual flat objects or groups of flat objects lying one upon the other) being conveyed overlapping one another, into at least one conveying stream of stream elements that do not overlap one another, but rather are conveyed one behind the other and possibly also beside each other. The inventive method and device are to allow a significantly greater degree of freedom regarding characteristics of the stream elements and their arrangement in the supply stream and in the at least one conveying stream to be established, than is the case for the known methods described above which serve the same purpose. In particular, it is to be possible to transform supply streams of overlapping groups each comprising flat objects of differing formats lying one upon the other or objects with the same format lying one upon the other not in the form of a regular stack, with a minimum of conditions regarding the arrangement of the objects in the groups and the arrangement of the groups in the supply stream. Nonetheless, the device to be created for the implementation of the method is to be simple and in particular is to be adaptable in an as simple as possible manner to varying characteristics of the stream elements of the supply stream and to different requirements made of the stream transformation.
According to the fundamental idea of the method of the invention, for transforming the supply stream being continuously conveyed in a conveying direction, first, the stream elements of the supply stream overlapping one another and advantageously being loosely supported are individually gripped and then they are differently displaced in a regular sequence transverse to the conveying direction. The spatial orientation of the stream elements thereby remains substantially unchanged so that, following the displacement, the stream elements can be released and can, for example, be conveyed away once again loosely supported. For gripping, displacing, and simultaneously conveying away the stream elements, these are not gripped in the zone of their leading edges, but rather at a location distanced in a conveying direction from the leading edge and advantageously being situated in the conveying direction approximately in the middle of the stream elements. The gripping location, as required, may include or not include a lateral element edge and is essentially the same for all stream elements of the supply stream. The sole condition to be imposed on the supply stream is that it must be possible to grip all stream elements in the same way and that the stream elements do not overlap one another at the gripping location, i.e. that the spacing of the stream elements in the supply stream is greater than half the length of the stream elements in the conveying direction.
For gripping, displacing, and simultaneous onward conveying, for every stream element an upper and a lower clamping element is provided. The stream element is gripped by being clamped between the clamping elements transverse to its flat expanse (for a loosely supported stream element: from above and from below). The upper and the lower clamping elements are conveyed in the conveying direction with the same, essentially constant speed as the supply stream and with, in conveying direction, a constant distance or spacing between one another which distance is substantially the same as the element spacing in the supply stream. In addition, the clamping elements are displaceable in a controlled manner to a varying degree transverse to the conveying direction. As still remains to be demonstrated, this ability of being displaced may be limited to the upper clamping elements, depending on the requirements regarding additional support of the stream elements during displacement and onward conveyance. In such a case, lower clamping elements are provided being assigned to different diverging tracks and being conveyed along these tracks.
Advantageously, the transverse displacement is implemented parallel to the flat expanse of the stream elements (for loosely supported stream elements: essentially horizontally) such that the stream elements following the displacement are arranged beside each other. In doing so a conveying stream is produced, in which the stream elements, for example, are conveyed behind and beside each other in a staggered manner, distanced from one another parallel to the conveying direction and transverse to the conveying direction, i.e. a conveying stream, which in a simple manner can be conveyed away by a single conveyor belt and which is especially suitable for packaging the stream elements with the help of a quasi endless packaging material supplied from a roll. Such packaging is, for example, described in the publication EP-1188670. The number of stream elements being conveyed beside each other in such a conveying stream is in essence freely selectable.
The displacement, however, may also be implemented transverse to the flat expanse of the stream elements (for loosely supported stream elements: vertically), wherein the stream elements have to have a sufficient flexibility for the displacement and wherein part streams arranged one above the other are produced, in which part streams the stream elements are conveyed one behind the other and, for example, with a distance between one another. The number of part streams that can be produced in such a manner is in essence freely selectable.
For being able to grip the stream elements in a location, which does not include an edge, the upper and the lower clamping elements are independent of one another, i.e., they are coupled to separate driving means. For gripping in a lateral edge zone, it is advantageous to combine each upper clamping element with one lower clamping element to form a clamp and to couple the clamps to a single drive means. The drive means for driving the clamping elements advantageously are chain pairs driven in circulation, wherein the two chains are arranged on two opposite sides of the supply stream each wherein guide links are arranged between the two chains. The guide links extend transverse to the conveying direction and each guide link carries a clamping element or a clamp being displaceable to and fro between the chains. The length of the guide links or the distance between the circulating chains, respectively, is matched to the distance transverse to the conveying direction to be established between the stream elements. Furthermore, the drive means comprise control means for controlling the different displacements of the clamping elements along the guide links in the predefined, regular sequence. If possible, the control means are designed as stationary cams.
The most important advantages of the stream transformation in accordance with the invention are that all stream elements of the supply stream can be gripped in essentially the same location and before the stream elements are moved relative to one another, that the gripping location can be located in a central zone (without involvement of an element edge), that, in the conveying stream to be established, a substantially freely selectable number of stream elements can be conveyed beside each other or an essentially freely selectable number of part streams can be established respectively, and that the spatial orientation of the stream elements is not altered so that, for example, stream elements being supplied in a loosely supported manner can be conveyed away again in a loosely supported manner after the stream transformation without the need of a further re-orientation. The advantages of the central gripping location, the advantage of the prevention of relative movement of stream elements not yet held gripped and the advantage of the spatial stream element orientation remaining unchanged are particularly relevant for stream elements that are groups of flat objects loosely lying on top of one another, and in particular for such groups in which the objects have different formats or in which the objects have similar formats but are not regularly stacked within the group.
It goes without saying that it is also possible to utilize the method and the device according to the invention for transforming supply streams comprising other stream elements, for example for transforming supply streams of individual objects all having the same format or of regular stacks of objects of the same format or also for transforming supply streams in which such stream elements do not overlap one another, but rather are conveyed one behind the other. In the same manner, while the method and the device according to the invention are very advantageous for establishing conveying streams in which the stream elements are at a distance from one another (i.e. do not overlap), it is equally possible to use the method and the device for producing streams in which the stream elements overlap one another, i.e. for changing the manner of the overlapping of the supply stream. It is further possible to use the method and the device according to the invention for splitting the supply stream into sections, i.e., into groups of overlapping stream elements, and to convey these away either beside or above one another.